Optocouplers contain at least one optical emitter device which is optically coupled to an optical receiver device through an optically transmissive medium. This arrangement permits the passage of information from one electrical circuit that contains the optical emitter device to another electrical circuit that contains the optical receiver device. A high degree of electrical isolation is maintained between the two circuits. Because information is passed optically across an insulating gap, the transfer is one way. For example, the optical receiver device cannot modify the operation of a circuit containing the optical emitter device. This feature is important because, for example, the emitter may be driven by a low voltage circuit using a microprocessor or logic gates, while the output optical receiver device may be part of a high voltage DC or AC load circuit. The optical isolation also prevents damage to the input circuit caused by the relatively hostile output circuit.
A common optocoupler package format is the dual-in-line package or DIP. This package is widely used to house integrated circuits and is also used for conventional optocouplers. Various versions of optocoupler DIP packages having 4, 6, 8 or 16 pins are commonly manufactured.
FIG. 1 shows a cross section of a conventional optocoupler DIP package 10. The illustrated optocoupler 10 includes a lead frame 24 comprising leads 24(a), 24(b) (i.e., pins). An optical emitter device 12 is mounted on one lead 24(a). An optical receiver device 14 is mounted on the other lead 24(b). The optical receiver device 14 generates an electrical signal after receiving light generated by the optical emitter device 12. The optical emitter device 12 is electrically coupled to the lead 24(a) through its bottom surface, and to another lead (not shown) via a wire 11. Similarly, optical receiver device 14 is electrically coupled to the lead 24(b) through the bottom surface and to another lead (not shown) via a wire 13. It will be recognized by those skilled in the art that the optical emitter device 12 operates with two electrical connections, an anode and a cathode. These connections are thus provided by the wire 11 and the lead 24(a). Similarly, optical receiver device 14 operates with two electrical connections, typically an emitter and a collector. These connections are provided by the wire 13 and lead 24(b). The optocoupler package 10 further includes an optically transmissive medium 16. A molding compound 18 encases the leadframe 24, optical emitter device 12, optical receiver device 14, and the optically transmissive medium 16.
A number of improvements could be made to the optocoupler package 10 shown in FIG. 1. For example, the optocoupler package 10 requires an expensive and time consuming overmolding process. In the overmolding process, the molding compound 18 encapsulates the other parts of the optocoupler package 10. In addition to the overmolding process itself, mold material removal processes (e.g., dejunk and deflash processes) are used to remove excess molding compound, thus adding to the time and expense of forming an optocoupler package. In addition, the tooling that is needed to create moldings of different xe2x80x9cform factorsxe2x80x9d (e.g., 4, 6, or 8 pin packages) requires a significant capital investment. Accordingly, if the overmolding process could be eliminated, the time and costs associated with producing optocoupler packages could be reduced.
Other improvements to the optocoupler package 10 could also be made. The optocoupler package 10 is also prone to failure from thermal cycling. For example, the difference in the thermal expansion properties of the molding compound 18 and the optically transmissive medium 16 causes them to expand and contract at different rates when they are heated and cooled. The molding compound 18 and the optically transmissive medium 16 could potentially separate, thus resulting in a structurally weak package. Temperature cycling also produces stress at the points where the lead frame 24 exits the molding compound 18 (e.g., at point xe2x80x9cAxe2x80x9d). The stress can result in a broken or weakened lead frame 24. Also, the wires 11, 13 can sometimes pass through the optically transmissive medium 16 and the molding compound 18. Differences in the thermal expansion properties of the optically transmissive medium 16 and the molding compound 18 can induce stress in the wires 11, 13 and can cause them to break.
It would also be desirable to reduce the height of conventional optocoupler packages. The optocoupler package 10 shown in FIG. 1 is relatively high. For example, the net height of a typical DIP package is about 3.5 to about 4.0 mm. It would be desirable to reduce the height of the optocoupler package so that it has a lower profile. By doing so, smaller electronic components could be produced.
Embodiments of the invention address these and other problems, individually and collectively.
Embodiments of the invention are directed to optocoupler packages, optocoupler assemblies, and methods for making the same.
One embodiment of the invention is directed to an optocoupler package comprising: a) a carrier substrate including a plurality of conductive regions; b) an optical emitter device on the carrier substrate; c) an optical receiver device on the carrier substrate; d) an optically transmissive medium disposed between the optical emitter device and the optical receiver device; and e) a plurality of solder structures on at least some of the conductive regions of the carrier substrate.
Another embodiment of the invention is directed to an optocoupler package comprising: a) a carrier substrate including a plurality of conductive regions; b) an optical emitter device on the carrier substrate; c) a first wire coupling the emitter device to at least one of the plurality of conductive regions; d) an optical receiver device on the carrier substrate, wherein the optical receiver device is adapted to receive radiation from the emitter device; e) a second wire coupling the optical receiver device to at least one of the conductive regions; f) an optically transmissive medium disposed on and between the optical emitter device and the optical receiver device; and g) a plurality of solder structures on at least some of the conductive regions in the plurality of conductive regions and wherein each of the solder structures includes a dimension greater than the heights of the optical receiver device and the optical emitter device.
Another embodiment of the invention is directed to an optocoupler apparatus comprising: a) a circuit substrate comprising a first plurality of conductive regions; and b) an optocoupler package comprising (i) a carrier substrate, (ii) a second plurality of conductive regions on the carrier substrate, (iii) an optical receiver device on the carrier substrate, (iv) an optical emitter device on the carrier substrate, (v) an optically transmissive medium disposed between the optical emitter device and the optical receiver device, and (vi) a plurality of solder structures on at least some of the second plurality of conductive regions of the carrier substrate, wherein the optocoupler package is mounted to the circuit substrate.
Another embodiment of the invention is directed to a method for forming an optocoupler package comprising: a) mounting an optical emitter device on the carrier substrate with a plurality of conductive regions; b) mounting an optical receiver device on the carrier substrate; c) forming an optically transmissive medium disposed on the optical receiver device and the optical emitter device; and d) forming a plurality of solder structures on at least some of the conductive regions of the carrier substrate.
Another embodiment of the invention is directed to a method for forming an optocoupler apparatus comprising: a) forming the optocoupler package according to the method of described above; and b) mounting the optocoupler package to a circuit substrate.
Another embodiment of the invention is directed to a surface mountable optocoupler package comprising: a) a carrier substrate including a plurality of conductive regions; b) an optical emitter device on the carrier substrate; c) an optical receiver device on the carrier substrate; d) an optically transmissive medium disposed between the optical emitter device and the optical receiver device; and e) a plurality of conductive structures on at least some of the conductive regions of the carrier substrate, wherein the surface mountable optocoupler package is capable of being mounted to a circuit structure
These and other embodiments of the invention are described in further detail below with reference to the Drawings.